Earth-orbiting satellites are now very numerous and provide a wide range of services, mostly in the areas of communications and remote sensing. These satellites find themselves immersed in a hostile environment of high-energy charged particles (electrons and ions) that originate in the Sun, are emitted as the “solar wind”, and eventually swirl around the Earth following complex paths that are strongly influenced by the Earth's magnetic field. Some of these charged particles enter the Earth's atmosphere to generate the visible aurora and others swoop past the Earth only to become involved in unstable oscillations that drive them backwards, once again towards the Earth. A fraction of all these particles eventually become trapped in relatively stable patterns known as the Van Allen belts (sometimes called “radiation belts”).
Unfortunately, the regions most heavily populated with high-energy charged particles are also the regions most frequently used by satellites, so that encounters between them are inevitable. In general, the impacts of most types of energetic charged particles are capable of causing either temporary or permanent damage to satellite electronic circuits. In particular, the electrons usually are not sufficiently energetic to pass through an entire satellite but they are energetic enough to become deeply embedded in the satellite dielectric materials that are used for both thermal and electrical insulation. There, the electric charge can build up to the point of electrical breakdown and arc discharge, producing both electromagnetic interference and physical damage. Wires or other conductors that are electrically “floating” (i.e. not grounded to the satellite frame) represent a special danger because they can store a large quantity of electrostatic energy which can be severely damaging when it discharges.
It has been determined that over 90% of the satellite anomalies that have occurred over the last 25 years are likely owing to environmental effects with at least 50% of the total owing to charging and discharging within the satellite (H. C. Koons et al., “The Impact of the Space Environment on space Systems”, The Aerospace Corporation, paper at the Spacecraft Charging Technology Conference, 2-6 Nov., 1997, Hanscom AFB).
Therefore, it would be very advantageous to provide satellite operators with sufficient warning of an impending discharge or breakdown, so that they can take mitigating measures to avoid problems. This necessitates providing a satellite charge monitor which is compact and can sense the voltage buildup in the dielectric materials representative of the dielectric materials from which the satellite is produced.